HV MOSFET Breakdown Voltage via Lateral Drain Segmentation
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Solution Overview
Problem
High voltage MOSFETs on silicon-on-insulator substrates face challenges in increasing breakdown voltage without thickening the insulating layer, which can lead to increased defect densities and degraded device performance.
Innovation Solution
Incorporating a lateral drain extension region with a breakdown voltage enhancing region of opposite conductivity type under it, which blocks majority carriers and increases the distance between them and the handle substrate, thereby enhancing the breakdown voltage without increasing the insulating layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the insulating layer thickness is increased to increase breakdown voltage, then the breakdown voltage is improved, but the defect density increases and device performance degrades
Solution Approach 1:
The patent divides the drain region into two segments: a first drain region directly over the insulating layer and a second drain region laterally offset from the first drain region. This segmentation allows the electric field to be distributed across two separate regions, enabling high breakdown voltage without requiring a thick insulating layer, thus avoiding increased defect density while maintaining device performance.
Solution Approach 2:
The patent transitions from a vertical field distribution (relying solely on insulating layer thickness) to a lateral field distribution by offsetting the second drain region laterally from the first drain region. This dimensional change allows the breakdown voltage to be enhanced through lateral spacing rather than vertical thickness, avoiding the need to thicken the insulating layer and thereby preventing increased defect density.
2Strength
If the insulating layer thickness is increased to increase breakdown voltage, then the breakdown voltage is improved, but the insulating layer thickness increases
Solution Approach 1:
The drain region is segmented into a first drain region and a second drain region positioned at different lateral locations. This segmentation enables the breakdown voltage to be determined by the lateral spacing between regions rather than the insulating layer thickness, allowing breakdown voltage enhancement without increasing the insulating layer thickness.
Solution Approach 2:
The patent shifts the breakdown voltage enhancement mechanism from the vertical dimension (insulating layer thickness) to the lateral dimension (offset distance between first and second drain regions). This dimensional transition allows breakdown voltage to be increased while maintaining a thin insulating layer, as the lateral spacing provides the necessary field distribution without requiring vertical thickness increase.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively increases the breakdown voltage of HV MOSFETs, preventing device failure from voltage breakdown and improving reliability, as demonstrated by the ability to withstand higher voltages without leakage current spikes.
Implementation Method 1
Incorporating a lateral drain extension region with a breakdown voltage enhancing region of opposite conductivity type under it, which blocks majority carriers and increases the distance between them and the handle substrate
Data Source
AI summary
An integrated circuit (IC) includes a high-voltage (HV) MOSFET on a substrate. The substrate includes a handle substrate region, an insulating region, and a silicon region. Source region and drain regions, which have a first conductivity type, are disposed in the silicon region and spaced apart from one another. A gate electrode is disposed over an upper region of the silicon region and is arranged between the source and drain regions. A body region, which has a second conductivity type, is arranged under the gate electrode and separates the source and drain regions. A lateral drain extension region, which has the first conductivity type, is disposed in the upper region of the silicon region and extends laterally between the body and drain regions. A breakdown voltage enhancing region, which has the second conductivity type, is disposed in the silicon region under the lateral drain extension region.